1. Field of the Invention
The present invention comprises a direction finding antenna system adapted for use with a two-channel monopulse system. In such a system, the low frequency limit of operation is determined by the quality and gain of the difference (.DELTA.) and sum (.SIGMA.) modes of the antenna system. This frequency may be so low that the antenna array diameter, D, is less than 2/3 wave length, i.e., D&lt;(2.lambda./3). The high frequency limit is determined by the size and tolerance of the center part of the antenna, in this case a spiral, so as to still have good gain and quality in the sum mode.
2. Description of the Prior Art
The prior art comprises conventional two-channel monopulse systems. One such system is a logarithmic spiral and array of towel bar antennas which are separately driven and not inter-connected in any way.